Based on a short discussion of circuit bending, Lars Kai Hansen, reminded me of the strange instrument reactable. Reactable is a music instrument based on synthesizer, but with a tabletop user interface on which the user can create different sounds by placing building blocks interacting with each other as a kind of electronic circuit. It is the result of a project under the Music Techynology Group at Pompeu Fabra University. On Wikipedia there is an entry, of oucrse, and on YouTube you can see two videos demonstrating the instrument: Video 1 and Video 2.